Power drills and hand drills utilize the rotational energy to rotate the bits in high speed for drilling articles. The spur of bits will grow dull after a period of utilization, and need to be sharpened. The lifetime of a bit can last longer if the sharpening procedure is accurate. There are two conventional sharpeners for drill bits commonly used in the field as follows:
Referring the structural drawing of FIG. 1, the indicated sharpener for hand drills comprises a body (1) including an axis (11) installed therein by a bearing (12) and it is parted as two portions enveloped by an axis sleeve (14) and an inner axis sleeve (111) respectively; an abrasive wheel (13) mounted on the axis sleeve (14); a base plate (15) with several annular aligned inserting holes (151) possessing different radii from 3.6-10 m/m; a beveled groove (152) positioned under the inserting holes (151) and the spur of bit can emerge therefrom to contact with the abrasive wheel (13); and a retainer (153) opposed to the beveled groove (152) to maintain a vertical position for the inserted bit. The chuck of the hand drill clamp on the inner axis sleeve (111) and then tightly mounted by a fitting (16). The drill bit needs to be sharpened is inserted in the inserting hole (151). The spur of the bit can emerge from the beveled groove (152) and contacts with the abrasive wheel (13) to ready for the sharpening procedure. The electrical power transmits to axis (11) when the hand drill is switched on, and it provides the co-axial rotation of the axis (11) and abrasive wheel.
The main drawback of this type of sharpener is that the distance between the base plate (15) and abrasive wheel (13) is not adjustable, and thus the length of the spur emerged from the beveled groove (152) is constant. Therefore, the spur may be over wear out during the sharpening procedure.
There is an another structure to provide an improved sharpener for the bits of drills according to the structure demonstrated in FIG. 1. Referring to FIGS. 2 and 2A, there is a fixing board (131) on the top end of the abrasive wheel (13) and a tray (132) contacted underneath, and they are connected by a screw (13) inside the axis (11). An adjustable tuning base (17) with a positioning groove (171) is mounted on the body (1) and its outer rim connects with the bottom end of the base plate (15). A steel balls (172) in the body (1) is used to adjust the positioning groove (171) on the tuning base (17) to give a proper gap for emerging the spur of drill bit. Additionally, the base plate (15) can be moved upward or downward together with the tuning base (17) to adjust the distance between the base plate (15) and abrasive wheel (13). The spur of the inserted drill bit is then to have an accurate contact with the abrasive wheel (13).
Both the above mentioned sharpeners are suitable sharpening the drill bit for hand drill only. However, there are disadvantages found for the above mentioned sharpeners, such as:
1. During the sharpening, the user should hold the hand drill and vertical press the bit simultaneous, and thus cause the difficulty while switching on and off the hand drill. PA0 2. The chuck of the power drill is vertical downward. The base plate (15) is face to the ground when the chock is locked by the fitting (16). It will cause the difficulty to observe the drill bit during the sharpening.
Therefore, there is a need to provide an improved drill bit sharpening apparatus which is suitable for sharpening the drill bits of both power drill and hand drill.